A fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium, and holmium. Fiber lasers can be used as high power, high repetition rate, ultrafast laser sources. Fiber lasers have advantages in efficiency, beam quality, and average power capability, but are limited in peak power due to nonlinear and damage effects.
Combining the outputs of many lasers to scale the energy output has been accomplished with continuous wave (CW) lasers using beam combination based on a diffractive optical beam splitter. This technique, however, cannot be used with ultrashort (e.g., ˜100 femtosecond (fs)) pulses due to angular dispersion and pulse front tilt.